Magnetically Assisted Direction-Changeable Roller Wrench

ABSTRACT

A magnetically assisted direction-changeable roller wrench has a main body, a driving member, a direction changing knob, plural rollers, a magnetic balancing member, and a magnetic positioning unit. The driving member, the rollers, and the direction changing knob are mounted in a head portion of the main body. The magnetic positioning unit includes a first and a second magnetic member located respectively on the driving member and the direction changing knob. The corresponding surfaces of the first and the second magnetic members have the same magnetic polarity, so a predetermined distance can be maintained between the first and the second magnetic members to secure the direction changing knob in position. The direction changing knob can displace each roller into contact with an engaging surface of the corresponding side of the driving member. The magnetic balancing member and the magnetic positioning unit lie in opposite directions to enable balanced magnetic attraction.

BACKGROUND OF THE INVENTION 1. Technical Field

The present invention relates to a wrench and more particularly to amagnetically assisted direction-changeable roller wrench whose operationdirection can be changed via a magnetic force and whose directionchanging components can be secured in position magnetically.

2. Description of Related Art

FIG. 1 shows a conventional direction-changeable roller wrench 10. Thehead portion 11 of the roller wrench 10 has a circular receiving chamber12 in which a driving member 14 is mounted. As shown in FIG. 2, thedriving member 14 has six sides 15, and each side 15 has a centralrecess 152 and two lateral sides each formed with an engaging surface151. Six rollers 16 are mounted respectively between the six sides 15and a peripheral wall 13 of the receiving chamber 12. A directionchanging knob 17 is mounted at the top end of the head portion 11. Thebottom side of the direction changing knob 17 is protrudingly providedwith six walls 171, and the gap between each two adjacent walls 171forms a position-limiting groove 172, i.e., a total of sixposition-limiting grooves 172 are formed. The six rollers 16 areconfined in the six position-limiting grooves 172 respectively, as shownin FIG. 2. The direction changing knob 17 is rotatable and can besecured at two positions by three magnetic positioning units 18, whereineach magnetic positioning unit 18 includes a pair of magnetic members.As shown in FIG. 1 and FIG. 3, the magnetic members of each of the threemagnetic positioning units 18 are mounted respectively on the bottomside of the direction changing knob 17 and the top side of the drivingmember 14. The corresponding sides of the magnetic members of eachmagnetic positioning unit 18 are of the same magnetic polarity.

The direction changing knob 17 can be switched from a first position toa second position by being rotated in a predetermined direction. Whenthe direction changing knob 17 is rotated to a position between thefirst position and the second position, referring to FIG. 3, themagnetic members of each magnetic positioning unit 18 are close to eachother, and the same magnetic polarity of the corresponding, and nowadjacent, sides of the magnetic members of each magnetic positioningunit 18 gives rise to a magnetic repulsive force that pushes the drivingmember 14 and the direction changing knob 17 away from each other. Oncethe magnetic members of each magnetic positioning unit 18 move past eachother, the same magnetic repulsive force pushes the direction changingknob 17 toward the second position until the magnetic members of eachmagnetic positioning unit 18 are no longer close to each other, i.e.,until the magnetic repulsive force between each pair of magnetic membersno more exists. As a result, each roller 16 is in contact with theengaging surface 151 on one lateral side of the corresponding side 15(e.g., the left engaging surface 151 of the corresponding side 15).Rotating the direction changing knob 17 in the opposite direction canswitch the direction changing knob 17 from the second position to thefirst position and thereby move each roller 16 to the other lateral sideof the corresponding side 15 and hence into contact with the engagingsurface 151 on that lateral side of the corresponding side 15 (e.g., theright engaging surface 151 of the corresponding side 15). During theprocess, the magnetic members of each magnetic positioning unit 18 willalso be brought close to each other, producing a magnetic repulsiveforce that pushes the direction changing knob 17 toward the firstposition. Thus, by switching the direction changing knob 17 to the firstposition or the second position, the operation direction of the rollerwrench is changed.

While the direction changing operations of the conventional rollerwrench 10 can be carried out with ease, the inventor of the presentinvention has found in his research that the three magnetic positioningunits 18 of the conventional roller wrench 10 may have problem beingeffectively operated, the reason being that the magnetic repulsive forceproduced by the multiple magnetic positioning units 18 is so great thatduring the direction-changing rotating process, it cannot be easilyovercome in order to switch the direction changing knob 17 to theintended position, and that the direction changing knob 17 may insteadbe moved back to its previous position by the magnetic repulsive force.

Moreover, the high cost of magnetic components adds to the material andproduction costs of the conventional roller wrench 10, which uses threemagnetic positioning units 18.

BRIEF SUMMARY OF THE INVENTION

The present invention aims to solve the aforesaid problems of the priorart, the primary objective being to provide a magnetically assisteddirection-changeable roller wrench whose operation direction can beeasily changed and whose direction changing components can be secured inplace with the same ease.

Another objective of the present invention is to provide a magneticallyassisted direction-changeable roller wrench that uses fewer magneticcomponents, and therefore has a lower cost, than its prior artcounterparts.

The present invention provides a roller wrench that includes a mainbody, a driving member, a direction changing knob, a plurality ofrollers, at least one magnetic positioning unit, and at least onemagnetic balancing member.

The main body has a head portion. A circular receiving chamber isprovided in the head portion, and the center of the receiving chamberdefines an axis.

The driving member has a plurality of sides, and each side has a centralregion and two engaging surfaces located respectively on two lateralsides of the central region. The driving member is mounted in thereceiving chamber of the head portion and can be rotated in thereceiving chamber about a rotation axis defined by the axis.

The direction changing knob is mounted in the head portion. Thedirection changing knob can be rotated between a first position and asecond position.

The rollers are provided in the receiving chamber. The directionchanging knob can drive the rollers into displacement.

The at least one magnetic positioning unit includes a first magneticmember and a second magnetic member. The first magnetic member islocated on the driving member, and the second magnetic member is locatedon the direction changing knob. The corresponding sides of the first andthe second magnetic members have the same magnetic polarity and cantherefore produce a magnetic repulsive force for securing the directionchanging knob at the first position or the second position.

The at least one magnetic balancing member is provided on the drivingmember or the direction changing knob. The magnetic balancing member andthe magnetic positioning unit are located on two opposite sides of theaxis respectively.

Preferably, the magnetic balancing member has a greater magnetic forcethan the first magnetic member or the second magnetic member.

The foregoing structures are so designed that fewer magnetic positioningunits are used between the direction changing knob and the drivingmember than in the prior art to assist the changing of direction, andthis reduces the magnetic repulsive force that must be overcome in adirection changing operation. Moreover, the magnetic balancing memberhelps balance the magnetic attractive force produced by the magneticpositioning unit, and the smaller number of magnetic components than inthe prior art contributes to a lower production cost.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The objectives, features, and effects of the present invention can bebetter understood by referring to the following detailed description ofsome preferred embodiments in conjunction with the accompanyingdrawings, in which:

FIG. 1 is a partial exploded perspective view of a conventional rollerwrench;

FIG. 2 is a partial assembled sectional view of the conventional rollerwrench in

FIG. 1;

FIG. 3 is a partial longitudinal sectional view of the conventionalroller wrench in FIG. 2;

FIG. 4 is a perspective view of the roller wrench according to apreferred embodiment of the invention;

FIG. 5 is a partial exploded perspective view of the roller wrench inFIG. 4;

FIG. 6 is a partial sectional view taken along line 6-6 in FIG. 4;

FIG. 7 is a top view of the driving member;

FIG. 8 is a bottom view of the direction changing knob;

FIG. 9(A) is a sectional view taken along line 9-9 in FIG. 4, showingthe direction changing knob moved toward a second position;

FIG. 9(B) is another sectional view taken along line 9-9 in FIG. 4,showing the direction changing knob moved toward a first position;

FIG. 10 is a partial assembled sectional view of the roller wrench inFIG. 4, showing the roller wrench rotated clockwise while the directionchanging knob is at the first position;

FIG. 11 is generally the same as FIG. 10, showing the roller wrenchrotated counterclockwise while the direction changing knob is at thesecond position;

FIG. 12 is a top view of the driving member in the second preferredembodiment of the invention, showing that the radial distance betweenthe magnetic balancing member and the axis is greater than the radialdistance between the magnetic positioning unit and the axis;

FIG. 13 is a partial assembled sectional view of the roller wrenchaccording to the third preferred embodiment of the invention, showingthat there are one magnetic positioning unit and two magnetic balancingmembers, and that the roller switch is rotated clockwise while thedirection changing knob is at the first position;

FIG. 14 is generally the same as FIG. 13, showing the roller wrenchrotated counterclockwise while the direction changing knob is at thesecond position;

FIG. 15 is a partial assembled sectional view of the roller wrenchaccording to the fourth preferred embodiment of the invention, showingthat there are two magnetic positioning units and one magnetic balancingmember, and that the roller switch is rotated clockwise while thedirection changing knob is at the first position; and

FIG. 16 is generally the same as FIG. 15, showing the roller wrenchrotated counterclockwise while the direction changing knob is at thesecond position.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 4 to FIG. 6, the roller wrench 20 according to apreferred embodiment of the present invention includes a main body 30, adriving member 40, a plurality of rollers 50, a direction changing knob60, a magnetic balancing member 70, and a magnetic positioning unit,wherein the magnetic positioning unit includes a first magnetic member46 and a second magnetic member 66.

The main body 30 has a head portion 31 and a shaft 36 connected to thehead portion 31. The head portion is located at the front end of theshaft. The top side of the head portion 31 is concavely provided with acircular receiving chamber 32, and the bottom side of the head portion31 is hollow, e.g., is provided with a through hole 34. The center ofthe receiving chamber 32 defines an axis C.

As shown in FIG. 7, the driving member 40 is a component of a regularpolygonal shape such as a square, a regular pentagon, a regular hexagon,or a regular octagon and has a plurality of sides. In the preferredembodiments disclosed herein, the driving member 40 is of a regularhexagonal shape by way of example and has six sides 41. Each side 41 ofthe driving member 40 has a central region 42 formed as a flat surface.Each side 41 is also provided with an engaging surface 44 on each of twolateral sides of the corresponding central region 42. Each engagingsurface 44 has an inner side 441 connected to the corresponding centralregion 42 and an outer side 442 located away from the correspondingcentral region 42. The driving member 40 is mounted in the receivingchamber 32 of the head portion 31 as shown in FIG. 5 and FIG. 6 and canbe rotated in the receiving chamber 32 about a rotation axis defined bythe axis C. The driving member 40 is configured to couple with and drivea threaded connecting element such as a nut or bolt into rotation, orcouple with a socket. The center of the driving member 40 may beprovided with a polygonal mounting hole for connecting with a threadedconnecting element. In this embodiment, the bottom side of the drivingmember 40 has an insertion post 45 extending out of the head portion 31through the through hole 34. The center of the driving member 40coincides with the axis C of the main body so that the insertion post 45can be rotated about a rotation axis defined by the axis C. The top sideof the driving member 40 is defined as a first side, and the firstmagnetic member 46 of the magnetic positioning unit is located on thetop side of the driving member 40, i.e., on the first side. The surfaceof the first magnetic member 46 may have the polarity of an N pole or Spole without limitation. The first magnetic member 46 has a magneticattraction area A1 and is spaced apart from the axis C by a radialdistance L1.

The number of the rollers 50 is equal to the number of the sides 41 ofthe driving member 40, so there are six rollers 50 mounted in thecircular receiving chamber 32. The rollers 50 are located respectivelybetween the six sides 41 and a peripheral wall 33 of the receivingchamber 32.

The direction changing knob 60 is mounted at the top side of the headportion 31 and closes the opening at the top side of the receivingchamber 32. The direction changing knob 60 is in the form of a circulardisk, and the center of the direction changing knob 60 coincides withthe axis C of the main body 30 so that the direction changing knob 60can be rotated about a rotation axis defined by the axis C. The bottomside of the direction changing knob 60 is peripherally provided with aplurality of walls that are arranged at equal intervals and whose numberis equal to the number of the rollers 50, i.e., a total of six walls 62are provided. In addition, there are six position-limiting grooves 64each formed between two adjacent walls 62. The six walls 62 are arrangedat equal intervals in a circular shape as shown in FIG. 8, and the sixrollers 50 are received, and thus confined, in the six position-limitinggrooves 64 respectively. The bottom side of the direction changing knob60 is defined as a second side. The first side of the driving member 40and the second side of the direction changing knob 60 face each other.The second magnetic member 66 of the magnetic positioning unit islocated on the bottom side of the direction changing knob 60, i.e., onthe second side. The surface of the second magnetic member 66 has thesame polarity as the first magnetic member 46, i.e., the first and thesecond magnetic members may both be N poles or S poles. The secondmagnetic member 66 has a magnetic attraction area A2 and is spaced apartfrom the axis C by a radial distance L2. The magnetic attraction area A1of the first magnetic member 46 and the magnetic attraction area A2 ofthe second magnetic member 66 are equal, and so are the radial distanceL1 between the first magnetic member 46 and the axis C and the radialdistance L2 between the second magnetic member 66 and the axis C. Thedirection changing knob 60 can be rotated between a first position and asecond position. When the direction changing knob 60 is rotated to aposition between the first position and the second position, the firstmagnetic member 46 and the second magnetic member 66 are so close toeach other that a magnetic repulsive force is produced between the firstmagnetic member 46 and the second magnetic member 66 due to thecloseness of two identical magnetic poles, and the direction changingknob 60 is pushed toward the first position or the second position as aresult.

The magnetic balancing member 70 in this embodiment is provided on thetop side of the driving member 40, i.e., on the first side, although itis also feasible to provide the magnetic balancing member 70 on thebottom side of the direction changing knob 60. The magnetic balancingmember 70 and the second magnetic member 66 are located on two oppositesides of the axis C respectively; in other words, the magnetic balancingmember 70 and the second magnetic member 66, which is in the same planeas the magnetic balancing member 70, form a central angle between 150°and 210° with respect to the axis C. In this embodiment, the aforesaidcentral angle is 180°. The polarity of the magnetic balancing member 70may be N or S without limitation. The magnetic balancing member 70serves mainly to attract the direction changing knob 60 magnetically.The magnetic balancing member 70 has a magnetic attraction area A3 andis spaced apart from the axis C by a radial distance L3. In thisembodiment, the magnetic attraction area A3 of the magnetic balancingmember 70 is larger than the magnetic attraction area A1 of the firstmagnetic member 46 and the magnetic attraction area A2 of the secondmagnetic member 66 in order for the magnetic balancing member 70 to havea greater magnetic force than the first magnetic member 46 and thesecond magnetic member 66 of the magnetic positioning unit.Alternatively, the magnetic balancing member 70 may be composed of amagnetic member having a greater unit magnetic force than the firstmagnetic member 46 and the second magnetic member 66 so that given thesame magnetic attraction area, the magnetic balancing member 70 canproduce a greater magnetic attractive force than the first magneticmember 46 and the second magnetic member 66. In this embodiment, theradial distance L3 between the magnetic balancing member 70 and the axisC is equivalent to the radial distance L1 between the first magneticmember 46 and the axis C and the radial distance L2 between the secondmagnetic member 66 and the axis C.

The following paragraphs describe certain states of use of the rollerwrench 20. The direction changing knob 60 can drive the rollers 50 intodisplacement and be secured at the first position or the second positionin order to switch the roller wrench 20 between different operationdirections. Take the directions shown in FIG. 4 and FIG. 6 for example.Rotating the direction changing knob 60 counterclockwise can switch thedirection changing knob 60 to the first position and thereby displacethe rollers 50 to the first position shown in FIG. 8, where each roller50 is in contact with the left engaging surface 44 a of thecorresponding side 41. Rotating the direction changing knob 60 clockwisecan switch the direction changing knob 60 to the second position andthereby displace the rollers 50 to the second position shown in FIG.9(A), where each roller 50 is in contact with the right engaging surface44 b of the corresponding side 41. To facilitate identification of thefirst position and the second position, the left engaging surfaces areindicated by the reference numeral 44 a, and the right engaging surfacesby the reference numeral 44 b. When referred to collectively, theengaging surfaces are indicated by the reference numeral 44.

In FIG. 10, the direction changing knob 60 and the rollers 50 have beenswitched to the first position, where each roller 50 is in contact withthe left engaging surface 44 a of the corresponding side 41. The secondmagnetic member 66 in this state is located on the left of the firstmagnetic member 46 to secure the direction changing knob 60 at the firstposition, with the rollers 50 limited to the first position by theposition-limiting grooves 64 of the direction changing knob 60.

The gap between each engaging surface 44 a and the peripheral wall 33 ofthe receiving chamber 32 is gradually reduced in an outward directionalong the outer side 442 of the engaging surface 44 a and is graduallyincreased in an inward direction along the inner side 441 of theengaging surface 44 a. When the rollers 50 are at the first position,rotating the wrench 20 clockwise will move each roller 50 toward theincreasingly narrow end of the gap associated with the correspondingengaging surface 44 a (i.e., outward along the corresponding outer side442) such that each roller 50 is engaged with the corresponding engagingsurface 44 a and the peripheral wall 33 of the receiving chamber 32,thereby allowing the wrench 20 to drive the driving member 40, and hencethe threaded connecting element coupled thereto, into clockwiserotation. Conversely, rotating the wrench 20 counterclockwise will moveeach roller 50 toward the increasingly wide end of the corresponding gapand thereby disengage each roller 50 from the corresponding engagingsurface 44 a and the peripheral wall 33 of the receiving chamber 32,making it impossible for the wrench to drive the driving member 40 intorotation. The engaging and disengaging effects described above enablethe wrench 20 to rotate a threaded connecting element in only onedirection (clockwise in this case).

When the direction changing knob 60 is rotated clockwise to the secondposition as shown in FIG. 9(A), the rollers 50 are driven by thedirection changing knob 60 to the second position and each end up incontact with the right engaging surface 44 b of the corresponding side41. When the direction changing knob 60 is moved to a position betweenthe first position and the second position, the second magnetic member66 on the direction changing knob 66 is so close to the first magneticmember 46 on the driving member 40 that a magnetic repulsive force isproduced between the first magnetic member 46 and the second magneticmember 66 because of the same magnetic polarity of the first and thesecond magnetic members 46 and 66. Once the second magnetic member 66 onthe direction changing knob 60 moves past the first magnetic member 46after being rotated from the first position, the magnetic repulsiveforce between the first magnetic member 46 and the second magneticmember 66 pushes the direction changing knob 60 to the second position.Since the first magnetic member 46 and the second magnetic member 66repel each other, the direction changing knob 60 will not be moved backto the first position. Now, with the first magnetic member 46magnetically attracted to the bottom side of the direction changing knob60 and the second magnetic member 66 magnetically attracted to the topside of the driving member 40, the direction changing knob 60 and thedriving member 40 are secured in position with respect to each othermagnetically. To keep the driving member 40 in balance, the magneticbalancing member 70 produces magnetic attraction on the opposite sideand is magnetically attracted to the direction changing knob 60 in orderfor the two opposite sides of the driving member 40 with respect to theaxis C to be subjected to magnetic attraction evenly, which prevents thedriving member 40 from tilting. As the magnetic attraction area A3 ofthe magnetic balancing member 70 is larger than the magnetic attractionarea A1 of the first magnetic member 46 and the magnetic attraction areaA2 of the second magnetic member 66, the magnetic attractive forcesacting respectively on the two opposite sides of the driving member 40are equivalent.

When the rollers 50 are secured at the second position as shown in FIG.11, rotating the wrench 20 counterclockwise will move each roller 50toward the increasingly narrow end of the gap associated with thecorresponding engaging surface 44 b (i.e., outward along thecorresponding outer side 442) such that each roller 50 is engaged withthe corresponding engaging surface 44 b and the peripheral wall 33 ofthe receiving chamber 32, thereby allowing the wrench 20 to drive thedriving member 40 into counterclockwise rotation. Conversely, rotatingthe wrench 20 clockwise will move each roller 50 toward the increasinglywide end of the corresponding gap and thereby disengage each roller 50from the corresponding engaging surface 44 b and the peripheral wall 33of the receiving chamber 32, making it impossible for the wrench todrive the driving member 40 into rotation. The engaging and disengagingeffects described above enable the wrench 20 to rotate a threadedconnecting element in only one direction (counterclockwise in thiscase).

Referring to FIG. 9(B), the direction changing knob 60 can be switchedfrom the second position to the first position in a way similar toswitching the direction changing knob 60 from the first position to thesecond position. The second magnetic member 66 on the direction changingknob 60 and the first magnetic member 46 on the driving member 40 arebrought close to each other when the direction changing knob 60 is movedto a position between the first position and the second positon. Oncethe second magnetic member 66 on the direction changing knob 60 movespast the first magnetic member 46 after being rotated from the secondposition, the magnetic repulsive force between the first magnetic member46 and the second magnetic member 46 pushes the direction changing knob60 to the first position. Since the first magnetic member 46 and thesecond magnetic member 66 repel each other, the direction changing knob60 will not be moved back to the second position. Now, with the firstmagnetic member 46 magnetically attracted to the bottom side of thedirection changing knob 60 and the second magnetic member 66magnetically attracted to the top side of the driving member 40, thedirection changing knob 60 and the driving member 40 are secured inposition with respect to each other magnetically. The magnetic balancingmember 70 also produces magnetic attraction on the opposite side and ismagnetically attracted to the direction changing knob 60.

Please refer to FIG. 12 for the second preferred embodiment of thepresent invention. The main structure of the second preferred embodimentis the same as that of the previous embodiment, and the identicalstructural features in the two embodiments are indicated by the samereference numeral and will not be described repeatedly.

The second preferred embodiment is different in that the magneticattraction area A3 and the unit magnetic force of the magnetic balancingmember 70 are respectively equal to the magnetic attraction area A1 andthe unit magnetic force of the first magnetic member 46 or the magneticattraction area A2 and the unit magnetic force of the second magneticmember 66, which makes the three magnetic members interchangeable, andthat in order for the magnetic balancing member 70 to produce strongermagnetic attraction than the first and the second magnetic members 46and 66, the radial distance L3 between the magnetic balancing member 70and the axis C is greater than the radial distance L1 between the firstmagnetic member 46 and the axis C and the radial distance L2 between thesecond magnetic member 66 and the axis C. The greater radial distance L3forms a longer moment arm when the magnetic balancing member 70 producesmagnetic attraction, thereby allowing a balance between the magneticbalancing member 70 and the first and the second magnetic members 46 and66 to be achieved.

Please refer to FIG. 13 and FIG. 14 for the third preferred embodimentof the present invention. The main structure of the third preferredembodiment is the same as that of the previous embodiment, and theidentical structural features in the two embodiments are indicated bythe same reference numeral and will not be described repeatedly.

The third preferred embodiment is different in that the roller wrench 20is provided with one magnetic positioning unit and two magneticbalancing members 70 between the driving member 40 and the directionchanging knob 60, wherein the magnetic positioning unit and the twomagnetic balancing members 70 are located on two opposite sides of theaxis C respectively. The two magnetic balancing members 70 are providedin the same plane and are both located on the first side, i.e., on thetop side of the driving member 40, lest a change in the distance betweenthe two magnetic balancing members 70 result in a magnetic repulsiveforce therebetween. Also, by disposing the first and the second magneticmembers 46 and 66 and the two magnetic balancing members on two oppositesides of the axis C respectively, each of the two opposite sides of theaxis C is provided with two magnetic components to enable uniformmagnetic attraction.

Please refer to FIG. 15 and FIG. 16 for the fourth preferred embodimentof the present invention. The main structure of the fourth preferredembodiment is the same as that of the previous embodiment, and theidentical structural features in the two embodiments are indicated bythe same reference numeral and will not be described repeatedly.

The fourth preferred embodiment is different in that the roller wrench20 is provided with two magnetic positioning units and one magneticbalancing member 70 between the driving member 40 and the directionchanging knob 60, wherein the two magnetic positioning units and themagnetic balancing member 70 are located on two opposite sides of theaxis C respectively. The magnetic attraction positions of the two firstmagnetic members 46 and of the two second magnetic members 66 are evenlydistributed, with the magnetic balancing member 70 provided on theopposite side to balance the overall application of magnetic attractiveforces. Moreover, the magnetic balancing member 70 and the two firstmagnetic members 46 are provided in the same plane, i.e., both on thefirst side, and the central angle formed between the magnetic balancingmember 70 and one of the two first magnetic members 46 with respect tothe axis C is generally equal to that between the magnetic balancingmember 70 and the other first magnetic member 46 to enable evendistribution of the magnetic attractive forces of the magnetic balancingmember 70 and of the two first magnetic members 46 and therefore uniformmagnetic attraction.

The roller wrench 20 of the present invention has the following effectsthat provide an improvement over its prior art counterparts. First, achange of direction can be achieved with at least one magneticpositioning unit (i.e., at least two magnetic members). Compared withthe prior art, which requires three magnetic positioning units (i.e.,six magnetic members), the magnetic repulsive force that must beovercome is reduced, meaning the direction changing operations will notbe hindered by an exceedingly great magnetic repulsive force.

Second, the wrench of the present invention uses fewer magneticcomponents than the prior art (i.e., at least one magnetic positioningunit and at least one magnetic balancing member) to enable a switch ofthe operation direction of the wrench and allow the direction changingcomponents to be secured in position after each direction changingoperation. Thanks to the reduction of use of magnetic components, theproduction cost of the wrench disclosed herein is lower than that of theprior art, which uses six magnetic members. Furthermore, the magneticbalancing member does not produce a magnetic repulsive force andtherefore does not add to the repulsive force produced by the magneticpositioning unit during a direction changing operation, lest thedirection changing operation be hindered by too great a repulsive force.

The embodiments described above serve only to expound the technicalfeatures, but not to limit the scope, of the present invention. Allsimple modifications and equivalent implementations based on thedisclosure of this specification and the appended claims shall fallwithin the scope of the patent protection sought by the applicant.

What is claimed is:
 1. A magnetically assisted direction-changeableroller wrench, comprising: a main body having a head portion and a shaftconnected to the head portion, wherein the head portion is providedtherein with a circular receiving chamber, and the receiving chamber hasa peripheral wall and has a center defining an axis; a driving member ofa regular polygonal configuration, wherein the driving member has aplurality of sides, each said side has a central region and two engagingsurfaces located respectively on two lateral sides of the centralregion, each said engaging surface has an inner side adjacent to acorresponding said central region and an outer side located away fromthe corresponding central region, and the driving member is mounted inthe receiving chamber of the head portion and is rotatable in thereceiving chamber about a rotation axis defined by the axis; a directionchanging knob mounted in the head portion, wherein the directionchanging knob is rotatable between a first position and a secondposition; a plurality of rollers corresponding in number to the sides ofthe driving member, wherein the rollers are located between theperipheral wall of the receiving chamber of the main body and thedriving member, the driving member is configured to drive the rollersinto displacement, each said roller is in contact with a said engagingsurface on a lateral side of a corresponding said side of the drivingmember and the peripheral wall of the receiving chamber when thedirection changing knob is at the first position, and each said rolleris in contact with a said engaging surface on an opposite lateral sideof the corresponding side of the driving member and the peripheral wallof the receiving chamber when the direction changing knob is at thesecond position; at least one magnetic positioning unit, wherein eachsaid magnetic positioning unit comprises a first magnetic member and asecond magnetic member, the first magnetic member of each said magneticpositioning unit is located on the driving member, the second magneticmember of each said magnetic positioning unit is located on thedirection changing knob, the first magnetic member and the secondmagnetic member of each said magnetic positioning unit havecorresponding surfaces of a same magnetic polarity, and the firstmagnetic member and the second magnetic member of each said magneticpositioning unit are able to generate a magnetic repulsive forcetherebetween such that the direction changing knob is secured at thefirst position or the second position by the magnetic repulsive forceafter being switched in position; and at least one magnetic balancingmember located on the driving member or the direction changing knob,wherein the at least one magnetic balancing member and the at least onemagnetic positioning unit are provided on two opposite sides of the axisrespectively.
 2. The roller wrench of claim 1, wherein the roller wrenchhas one said magnetic positioning unit and one said magnetic balancingmember, and the magnetic balancing member and the first or the secondmagnetic member in a same plane as the magnetic balancing member form acentral angle of 150° to 210° with respect to the axis.
 3. The rollerwrench of claim 1, wherein the roller wrench has two said magneticpositioning units and one said magnetic balancing member, and themagnetic balancing member and the two first or second magnetic membersin a same plane as the magnetic balancing member form generally equalcentral angles with respect to the axis.
 4. The roller wrench of claim1, wherein the roller wrench has one said magnetic positioning unit andtwo said magnetic balancing members, and the two magnetic balancingmembers are located concurrently on the driving member or the directionchanging knob.
 5. The roller wrench of any of claims 1 to 4, wherein theat least one magnetic balancing member is provided on the drivingmember.
 6. The roller wrench of any of claims 1 to 4, wherein the atleast one magnetic balancing member is provided on the directionchanging knob.
 7. The roller wrench of any of claims 1 to 4, wherein theat least one magnetic balancing member has a greater magnetic force thanthe first magnetic member or the second magnetic member of the at leastone magnetic positioning unit.
 8. The roller wrench of claim 7, whereineach said magnetic balancing member has a larger magnetic attractionarea than each said first magnetic member or each said second magneticmember.
 9. The roller wrench of claim 7, wherein each said magneticbalancing member has a greater unit magnetic force than each said firstmagnetic member or each said second magnetic member.
 10. The rollerwrench of any of claims 1 to 4, wherein a radial distance between eachsaid magnetic balancing member and the axis is greater than a radialdistance between each said first magnetic member or each said secondmagnetic member and the axis.
 11. The roller wrench of any of claims 1to 4, wherein the driving member has a side facing the directionchanging knob and defined as a first side, each said first magneticmember is provided on the first side, the direction changing knob has aside facing the driving member and defined as a second side, each saidsecond magnetic member is provided on the second side, the first sidefaces the second side, and each said magnetic balancing member islocated concurrently on the first side or the second side.